This disclosure relates to a display device with a touch detection function, and in particular, to a display device with a touch detection function detecting touch events based on a change in an electrostatic capacitance caused by an external proximity object, and an electronic unit including such a display device with a touch detection function.
In recent years, a display device capable of inputting information by mounting a contact detection device, which is a so-called touch panel, on a display device such as a liquid crystal display device, or integrating the touch panel and the display device, and displaying various button images and the like on the display device instead of typical mechanical buttons has attracted attention. The display device including such a touch panel does not require input devices such as a keyboard, a mouse, and a keypad, and therefore there is a tendency to expand the use of such a display device to portable information terminals such as mobile phones, in addition to computers.
As a method used in a touch detection device, some methods such as optical method and a resistance method exist. However, an electrostatic capacitance type touch detection device is promising which has a relatively simple configuration, is capable of detecting touch events at plural positions at a time, and is capable of achieving low power consumption which is considerable particularly for mobile terminals or the like. For example, Japanese Unexamined Patent Application Publication No. 2008-129708 (JP-A-2008-129708) discloses a touch detection device including a plurality of X-direction electrodes and a plurality of Y-direction electrodes which is disposed to face the X-direction electrodes, and detecting touch events with use of a change of an electrostatic capacitance caused by an external proximity object, the electrostatic capacitance being formed at each intersection between the X-direction electrodes and the Y-direction electrodes. In addition, for example, in Japanese Unexamined Patent Application Publication No. 2009-244958 (JP-A-2009-244958), a display device incorporating a touch detection function, in which a common electrode for display originally provided in the display device is shared as one of a pair of electrodes for a touch sensor, and the other of the pair of the electrodes (touch detection electrode) is disposed to intersect with the common electrode has been proposed.
Typically, measures against electro static discharge (ESD) are important in electronic units. Static electricity is possibly applied to an electronic unit, for example, in manufacturing the electronic unit and in its use by a user. For a touch detection device, some ESD protection measures have been proposed. For example, in Japanese Unexamined Patent Application Publication No. 2009-86077 (JP-A-2009-86077), a display device mounted with a resistance film type touch detection device on a liquid crystal display panel has been described. In the display device, to eliminate static electricity generated at the time of bonding a polarizing plate in manufacturing process of the liquid crystal display panel, a transparent conductive film is formed on the liquid crystal display panel so as to be in an electrically floating state, and after the polarizing plate is bonded, a jig is allowed to be in contact with the transparent conductive film.